Asymptotic lifting for completely positive maps
Abstract
Let and be -algebras with separable, let be an ideal in , and let be a completely positive contractive linear map. We show that there is a continuous family , for , of lifts of that are asymptotically linear, asymptotically completely positive and asymptotically contractive. If is of order zero, then can be chosen to have this property asymptotically. If and carry continuous actions of a second countable locally compact group such that is -invariant and is equivariant, we show that the family can be chosen to be asymptotically equivariant. If a linear completely positive lift for exists, we can arrange that is linear and completely positive for all . In the equivariant setting, if , and are unital, we show that asymptotically linear unital lifts are only guaranteed to exist if is amenable. This leads to a new characterization of amenability in terms of the existence of asymptotically equivariant unital sections for quotient maps.
Cite
@article{arxiv.2103.09176,
title = {Asymptotic lifting for completely positive maps},
author = {Marzieh Forough and Eusebio Gardella and Klaus Thomsen},
journal= {arXiv preprint arXiv:2103.09176},
year = {2025}
}
Comments
v2: 25 pages